Gaining an understanding of the catalytic mechanism and regulation of prostaglandin synthase is fundamental to a description of the inflammatory and thrombolic processes involved in arthritis, auto-immune responses, heart attack, and stroke, and to the development of rational therapies. The studies proposed here are intended to elucidate the structural basis for several important aspects of the enzyme's behavior. These aspects include the ability of one polypeptide to catalyze both cyclooxygenation and reductive peroxidation, activation of cyclooxygenase activity by peroxide, self-inactivation of the enzyme during catalysis, and the irreversible inhibition of the enzyme by several anti-inflammatory drugs. For a model system to study the behavior of the synthase in a membrane, the pure enzyme will be incorporated into phospholipid vesicles. The investigations will entail the use of spectral analysis of the enzymes (including spectrophotometry, magnetic circular dichroism, and electron paramagnetic resonance), and physical, chemical and biochemical techniques for analysis of protein structure.